A semiconductor wafer is a thin, round slice of semiconductor material, typically silicon, on which microchips are made. Manufacturers process silicon into large cylindrical masses of metal, slice the masses into wafers and then form transistors and other elements on the wafer before cutting the wafers into smaller semiconductor chips. A higher density of these semiconductor chips on the wafers is desirable for cost savings and productivity improvement. Chip manufacturers have made steady improvements in shrinking die size (i.e., chip size) and expanding wafer size. Manufacturers have also given more rows and columns to the lead frame matrix in assembly processes.
As is known, a number of semiconductor chips will fail after a relatively short period of operation. Such a failure is termed in the field as infant mortality. Semiconductor chips are subjected to heat and electric signals to cause infant mortality failures. The remaining semiconductor chips will exhibit improved reliability. Semiconductor devices must undergo a process commonly known as final testing. Final testing is the final process of an electrical testing of a semiconductor device. The final process involves using an automatic test handler, test contact and tester. The semiconductor chips are invented to strip out lead frames. This provides easier handling and handling of multiple semiconductor chips with a single touch. However, the strip format or strip base package cannot perform other testing, such as burn-in or signal cycling (e.g., read/write endurance testing).
FIG. 1A (Prior Art) is a conventional test/burn-in socket for a singulated semiconductor package. A singulated package is a unit semiconductor device which was assembled into a strip leadframe and then singulated out of lead frame into a single semiconductor chip. The test/burn-in socket includes a cover 102 and a base 104. The socket can also be used without a cover 102. A conventional test typically involves a test method used in conjunction with an automated handler which handles the semiconductor package which has already been singulated. Appropriate electronic signals are coupled to the semiconductor device to determine whether it is operational with predetermined specifications.
FIG. 1B (Prior Art) is a cross-sectional view of the conventional test/burn-in socket of FIG. 1A (Prior Art). The socket commonly has a socket body designed to accommodate a singulated semiconductor package 108. Electrical contacts of the package 108 are in electrical contact with corresponding electrical contacts of the socket body. The package 108 is under test in the test/burn-in socket.
In this singulated package 108, a lead 107 is formed into an appropriate shape. The base 104 of the socket is secured to the printed circuit board (PCB) 106 with contact pins 110. Numerous contact pins 110 contact the lead 107 or terminal of the package 108 for establishing an electrical connection between the PCB 106 and the package 108. Examples of a contact pin include a stamped pin 112 and a pogo pin 114.
FIG. 1C (Prior Art) is a conventional test/burn-in board, including multiple test or burn-in sockets. The test/burn-in board includes multiple sockets mounted on a PCB 106. A card edge connector 116 is integrally formed with the PCB 106. The card edge connector 116 is integrally for connecting the test/burn-in board to a test/burn-in system.
FIG. 7A (Prior Art) is a flowchart of an exemplary conventional testing/burn-in process. The process flow begins in operation 702 which includes assembly of semiconductor chips into packages. Assembly includes die attachment, wire bonding, plating and molding. The process flow proceeds to the operation 704 which includes forming the lead frame and singulation of the packages. Next, test/burn-in of singulated sockets is performed in the operation 706. In the operation 708, final testing is performed. Then, in operation 710, the devices which pass final testing are packed for shipping. As shown in FIG. 7A, only the operations 702 and 704 involve handling the packages as lead frames or strips. Operations 706, 708 and 710 involve handling the devices as singulated units.
Unfortunately, a conventional test/burn-in socket for a singulated package has inherent physical limitations that cause problems in a testing/burn-in process. The method of testing and burn-in of packages 108 is time consuming because numerous packages 108 must be individually loaded and unloaded. The method of testing and burn-in can also potentially create contact terminal defects, such as bending and causing coplanarity problems to the leads 107.